Pitotube routing hole...

[Peter_SE]

I’m currently restoring a model 2 Kitfox and now I am recovering the wing.

I also decided to replace the pitotube as it is 26 years old....the previous owner had drilled a hole through the Aluminium wing bar and routed the tube there in to the cockpit.

I enlarged the hole slightly to fit the new tube...but then I started thinking if this could affect the strength of the wing bar?

Is reinforcement with aluminium sheet now required or some other sort of reinforcement or is it not necessary?

https://uploads.tapatalk-cdn.com/20200216/104d49ba8d7d1f2cd0d6afbab9845575.jpghttps://uploads.tapatalk-cdn.com/20200216/aba2a30f67a16c00cfc920d677b65413.jpghttps://uploads.tapatalk-cdn.com/20200216/7c6aac092d2d65d594f95a745c164cf0.jpg


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[Peter_SE]

I found this in the build manual so I guess it is ok then?

https://uploads.tapatalk-cdn.com/20200216/32cbb6c8cc7cfbe7bb0ed193293561f1.jpg


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[Delta Whisky]

If I'm seeing the pictures correctly:

1. It appears that the builder followed the instructions.
2. The hole appears to be on the neutral axis.

And,

1. if it isn't larger than17/64 in height, and
2. there aren't any sharp edges or burrs,

You should be good to go.

[Peter_SE]

The hole is slightly bigger now on the highest point, 11.5 mm in height.

Maybe email kitfox and get opinion?

[Delta Whisky]

I'm not familiar with the rib numbering convention for the Model 2. Is the hole inboard or outboard of the lift strut attachment?

[Peter_SE]

The hole is inboard from the attachment.

I emailed kitfox and they don’t recommend any drilling in the spar.

Deaney Aircraft however did...Kitfox recommended structural repair according to Ac 43-13


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[Delta Whisky]

The inboard loads on the spar of a strut braced, high wing aircraft are a tad more complex that one might think; maybe there is someone lurking here that has the background to supply enough information to help you make a decision. Clearly Denny aircraft called for the hole but the issue now is that it is larger - how much larger is too much larger? That is the question. I couldn't spend much time in AC43-13 this evening but I couldn't find any instruction related to repairing a spar, let alone a round spar. My only suggestion is to see if you can get in touch with a DER (or, equivalent) for his/her advice or analysis. It may cost you a bit but might be a lot cheaper than the time and cost of a new spar/wing panel. Or, maybe a structures engineer is reading this and can assist.

[Peter_SE]

I have decided to to replace the spar, the other wing has a dent in the front spar as well so will be replacing that one to.


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[Delta Whisky]

I'm sure you put a lot of effort and time into making the decision and it wasn't easy - BUT - I'll bet you'll sleep better. Keep us posted on progress through your rebuild.